Method of treating copper alloy castings



Patented May 13, 1941 UNITED STATES PATENT. OFFICE METHOD OF TREATINGCOPPER. ALLOY CASTINGS Franc R. Hensel and Earl I. Larsen, Indianapolis,Ind., assignors to R. R. Mallory & Co. Inc., Indianapolis, had, acorporation of Delaware No Drawing. Application August 12, 1938, SerialNo. 224,497

2 Claims.

This invention relates to the production of copper alloy castings,containing high percentages of copper.

It is an object of the invention to produce castings of improvedhardness, electrical and structural parts and in the mechanical held,in-

applications where. high thermal conductivity is required, together withimproved strength. It is a further object of this invention to producecastings which will not anneal at elevated temperatures.

It is a further object of this invention to produce castings which havea high ratio of elastic limit to tensile strength.

Another object of the present invention is to produce castings which canbe readily brazed, soldered or welded, without destroying their physicalproperties.

Other objects will be apparent from the following description, taken inconnection with the appended claims.

The present invention comprises a combination of elements, methods ofmanufacture and the product thereof, brought out and exemplified in thedisclosure, hereinafter set forth, the scope of the invention beingindicated in the appended claims.

While a preferred embodiment of the invention is described herein, it iscontemplated that considerable variation may be made in the method ofprocedure and a combination of elements, githout departing from thespirit of the inven- In the prior art, alloys have been describedcontaining hardening elements, such as the silicides of the iron groupmetals. harden materials of this type, it has been necessary to apply adouble heat treatment, the first part of which is generally classifiedas a solution treatment, and which consists in heating the material to ahigh temperature and then rapidly quenching. In addition to this firsttreatment, a second treatment is employed, comprising a prolongedheating at a lower temperature. This is usually called the aging orprecipitation treatment because this treatment causes the decompositionof a super-saturated solid solution, the precipitated particles being sosmall in most cases that they cannot be detected under a microscope.

Heretofore, attempts have been made to manu- I iacture castingscommercially 01' copper hard- In order to ened with nickel silicide,using the double heat treatment of the prior art just described. Theresult was such a large number of failures of the castings thatmanufacture of this alloy was discontinued.

We have found that for many uses the above double heat treatment willnot produce the desired results when applied to copper alloys hardenedwith nickel or cobalt silicide.

While the castings show a considerable increase in hardness andconductivity, after such a double treatment, at the same time theybecome, very frequently, extremely brittle, and show very low tensilestrength. In a large number of castings treated that way, the ultimatetensile strength was only 5,000 p. s, i., and in many instances, it wasso low that the castings broke as a result of this heat treatment.Numerous tests were made, in which melting conditions and alloyingconditions were variedffiowever,

the inconsistency of physical properties could not be eliminated orcorrelated with composition. In addition to copper and nickel silicide,other elements were added, such as magnesium, aluminum, zinc, tin,phosphorus and cadmium, in percentages up to 5% without, however,resulting in improvement of the ultimate strength as long as the doubleheat treatment was employed.

We then made experiments in which the heat treatment was completelychanged in such a manner that the solution treatment was entirelyeliminated and only a single heat treatment, corresponding to an anneal,was used. The result was that hardness values could be obtained closelyapproaching those and in some cases equivalent to the ones obtained withthe double heat 1 treatment. The electrical conductivity, resulting fromthe single annealing treatment, was

additions of nickel and silicon, are approximately as follows:

Tensile strength p. s. i.-- 60,000 Brinell hardness -200 Electricalconductivity ..per cent 40-45 The ductility is a function of thechemical composition only and will vary from 5 to 35%, after ourannealing treatment.

The process of annealing is applied to sand castings or chill castings,irrespective of cross section. It usually consists in heating alloys forthe present invention can be prepared without taking any specialprecautions. Usually the copper is melted first, then the alloyadditions are made, preferably in the form of a suitable hardener andthe melt is poured in either sand, chill or other molds. The castingsshould then be used without any application of hot working because suchhot working operationswill partly destroy the beneficial eifect of thesingle heat treatment described in this application.

The castings prepared as indicated above are well suited for such partsas electrode wheels, current carrying members, heat carrying members,axles, shafts and corrosion resistant parts.

The preferred composition of the castings is as follows:

. v Per cent Nickel 0.5 to 5 Silicon 0.1 to 2 Copper Balance It ispossible likewise to improve alloys containing small percentages ofaditional ingredients by the single heat treatment described above; thuscopper alloys containing nickel and silicon may also contain suchelements as zinc, tin, silver, cadmium, magnesium, beryllium, aluminum,-titanium, zirconium, chromium, manganese, iron and cobalt.

While the present invention, as to its objects and advantages, hasbeen'described herein as carried out in specific embodiments thereof, itis not desired to be limited thereby, but it is intended to cover theinvention broadly, within the spirit and scope of the appended claims.

What is claimed is:

l. The method of improving the properties of copper which comprisesalloying with copper 0.5 to 5% of an element selected from the groupconsisting of nickel and cobalt and 0.1 to 2% silicon, casting theresulting alloy and then annealing the alloy in the as cast condition ata temperature between 400 C. and 600 C. for a period of from severalminutes to several hours to improve the hardness and tensile strength.

2. The method of improving the physical properties and particularly thetensile strength of castings consisting of 0.5 to 5% nickel, 0.1 toi 2%silicon and the balance copp r which comprises applying a single heattreatment to said castings in the as cast condition, said heat treatmentconsisting of an anneal for a period of from several minutes to severalhours at a temperature within the range 400 C. and 600 C.

FRANZ R. I-IENSEL.

EARL I. LARSEN.

